Autism and other pervasive developmental disorders
Symptomatology and diagnostic criteria
Characterized by a symptom triad
1. Communication deficits
2. Impaired social interaction
3. Restricted and stereotyped behaviours and interests
Onset is in early infancy.
Social and communicative impairments include
• Lack of exploration of faces and appreciation of other communicative signals
• Avoidance of eye contact
• Inability to monitor other people’s gaze direction
• Developmental delay of the ability to appreciate other people’s mental states
in term of beliefs, desires, knowledge, intentions, and dispositions.
• Lack of empathy
• Impaired ability to imitate observed behaviours
The severity of autistic spectrum disorders can vary from mild forms such as
Asperger’s Syndrome or highfunctioning autism or severe forms such as Kanner
autism which is associated with mental retardation (in approx two thirds of cases with
Kanner autism) or epilepsy (onethird).
Some individuals with autism have extraordinary skills in divergent domains such as
calendar calculation, music, drawing, etc. These savants are usually intellectually
The prevelance of autism in the general population is 3 to 6 per 1,000. The male to
female ratio is about 3 to 4:1.
There has been a slight increase in the number of diagnosis as a result of the changes
in case definition and diagnostic sensitivity.
Genetic risk factors
Autism is highly heritable such that the risk to develop the disorder is 30 to 120 times
higher for siblings of autistic children compared to the general population.
Risk for MZ twins is between 40% and 90%, and between 0% and 10% for DZ twins.
Theoretical models suggest that paternal or maternal imprinting could lead to an
overexpression of male characteristics in the brain and social cognitive impairments.
Environmental risk factors
The relative risk for developing autism is increased in individuals with: • Tuberous sclerosis
• Fragile X syndrome
• Prenatal rubella
• Prenatal exposure to toxins
These factors account for less than 10% to 15% of cases.
Higher parental age may also be associated to the onset of the disorder.
The pathophysiology of autism is poorly understood. BDNF may be upregulated in
the autistic brain, whereas apoptosis (programmed and selective cell death – this may
account fo the increased number of small densely packed neurons in some of the parts
of the autistic brain which are disconnected with the rest of the brain) is reduced.
Oxytocin (mediator of social cognition, bonding and sexuality) is downregulated.
Reduced serotonin levels in mothers of autistic children have been related to
alterations of brain development and maturation.
Hypothesized that the mirror neuron system, which is considered critical for imitation
learning and probably contributes to the simulation of other people’s states of mind
may be functionally impaired in individuals with autism.
Ethological observation of autistic children suggests, at least in some milder forms of
the disorder, a motivational conflict between approaching a caregiver and avoidance,
perhaps due to enhanced timidity and fear.
Avoidance of close contact is evident from very early on.
Insecure attachment styles are found to be more prevalent in autistic children
compared to healthy controls.
Parents of autistic children are on average no less sensitive than parents of normally
Autistic schoolage children, including those with highfunctioning autism and
Asperger’s syndrome engage less in social play and experience more often social
As adults, they have profound difficulties in establishing close social relationships or
Autistic individuals have problems understanding
• Intentions • Feelings
• Dispositions of others by making inferences about their mental states >
“Mentalizing” or “Theory of mind”
Selective impairment of social information processing including mentalizing, emotion
recognition and face processing.
Mentalizing deficits in autism, are, however, not directly linked to intelligence.
Social cognitive functioning involved in mentalizing emerges in children in distinct
developmental steps but impaired mentalizing is not enough to explain social
aloofness in autism.
Learning by imitaion is linked to the activity of specific meuronal cell populations
called mirror neurons.
Mirror neurons are even active when the outcome of a movement is hidden from
Imitating behaviour ad stimulating mental states have in common the ability to
imaginatively take the perspective of another individual.
Imitation and o